GaN semiconductor devices such as, for example, light emitting diodes (“LEDs”), laser diodes, photodetectors, transistors, switches, and so forth, are widely used in many applications. Well known applications include, but are not limited to, traffic signals, mobile telephone display backlighting, liquid crystal display (“LCD”) back lighting, flash lights for cameras, and so forth. The fabrication of gallium nitride semiconductors for use as LEDs, laser diodes or lighting, gives relatively low productivity.
There have been many proposals for the removal of a sapphire substrate from semiconductor light emitting devices by use of a laser. However, in all instances either the semiconductor layers (normally including epitaxial layers) crack thus significantly reducing yield; or the semiconductor layers are separated into individual devices prior to removal of the substrate. It has not been possible to remove the substrate by laser lift-off for the entire wafer without cracking, or separation before removal.